Rheostat



May 22, 1923. 1,455,903

W. G. CLARK RHEOSTAT Filed lay 9, 1921 3 Sheets-Sheet 2 .3 ZV-.5. 6J 5? di@ j 5:9 v :i0 n- 2 1 Il l I r E 7g I e L I.: l i il? -71 z 4 L i g fr z 61 mv a l Patented May 22, 1923.

UNITED STATES WILLIAM GUY CLARK, 0F OAK PARK, ILLINOIS.

RHEOSTAT.

Application led May 9,

To all whom it 'may concern:

Be it known that I, lVlLLiAM GUY CLARK, a citizen of the United States, residing :it Oak Park, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Rheostats, of which the following is a specification.

My invention relates to electric rheostats in general, but pertains more particularly to the manufacture and construction of such appliances using sheet-metal or similar grids secured together face to face in spaced relation, such as are ordinarily used in large quantities as resistance devices in connection with the electric motors of electric-cars of various types wherein the change of electrical resistance effected by the manuallyoperated controller governs or regulates the speed of travel of the ear.

One object of my invention is the production of such resistance grids with less metal or smaller blanks than has heretofore been customary, with, of course, a resulting economy in the cost of manufacture.

Another aim of the invention is the association of such grids together in such a manner that they cannot become deformed or warped under heat and touch one another thus short circuiting the rheostat at least in part. i

To enable those skilled in this art to have a full and complete understanding of the invention, I have illustrated several embodiments of the samein the accompanying drawings -forming a part of this specification and to which reference should be had in connection with the following detailed description, like reference characters being used throughout the several views to designate the same parts.

In these drawings; t

Figure 1 is a fragmentary vertical section through a portion of the improved rheostat or electrical resistance applianee`\on a line correspondingto line 1 1 of Figure 2;

Figure 2 isa face view of one of the sheetmetal grids or unit resistance elements illustrating in one part the supporting rod, its insulation sleeve, and the associated'metallic and insulation washers;

Figure 3 is a similar view of a blank eut and punched as shown'for the production of another embodiment of the invention;

Figure 4 is a face view of the completed unit or. grid, one portion being shown as 1921. serial No. 468,134.

ure 4;

Figure 7 is a section on line 7 7 of Figure 4;

Figure 8 is a section on line 8 8 of Figure 4;

Figure 9 is a face view of a blank upon which certain operations have been performed and from which a still different embodiment of the invention is made;

Figure 10 illustrates the completed grid in side elevation and shows one of the spacers used between the grids;

Figure 11 is a vertical edge view of the grid of Figure 10;

Figure 12 is a vertical section on line 12--12 of Figure 10;

Figure 13 is a section on line 13 13 of Figure 10; and

Figure 14 is a section on line 14-14 of Fi ure 10. v

eferring first to Figures 1 and 2, it will be perceived that the completed, flat, sheetmetal, steel grid or resistance unit of proper size and composed of suitable ingredients to provide the desired `resistance can be made from a rectangular blank with praetically no waste of metal, except such as is cut out to separate portions of the element to prevent their contact with one another.

In the production of such a member 20, it is punched to remove narrow strips of metal to provide the two, longitudinal, spaced, slots 21 and 22 extended inwardly part way only of the length of the grid from its lower edge, and to provide three other lengthwise slots 23, 24 and 25, the latter vonly extending inwardly from the upper edge of the grid midway between the slots 2l and 22, and a cross slot 26 intersecting slot 25 and connecting together the upper ends of the two outer slots 23 and 24, all as is clearly depicted in Figure 2.;

Thus there is provided a flat, sheet-metal,

resistance element having a pair of outer or marginal strips 28 .and 29 yequipped at their upper ends with inwardly-facing opposed ears ory lugs 30 and 31, eachdesirably suplied with a round aperture 32 for the usual astenings and supports.

The other or opposlte ends of such OlI1tv101sl side sections are connected together by a retlexed portion or strip .composed ot tour spaced parallel parts 33, 34, and 36 connected together as two pairs at their upper ends at 37 and 38, the parts 34 and 35 bcing connected together at their lower ends at 39, the side strips and 36 being united at their lower ends at and 41 to the corresponding portions of the marginal lengths 28 and 29.

Part 39 is supplied with a hole 42 for an electrical connection at this point, and the sect-ions 40 and 41 are equipped with smaller holes 43 and 44 for the accommodation of spacing means as is customary to prevent their warping sidewise when heated into contact with one another.

Heretofore it has been usual to make grids of this general type with the ears 30 and 31 extended outwardly in opposite directions from the strips 28 and 29 and to have the intermediate parts 33, 34, 35 and 36 extend the full length of the resist-ance unit,

providing holes in the parts corresponding to the portions 37 and 38 of the present structure for the accommodation of spacers to prevent these parts from touchin the corresponding portions of the next grids.

By employing the new structure, a substantial savin of metal is secured because no removal oi metal from the sides of the blank is required and there is a saving in punching operations in not needing the holes referred to.

Each of holes 32 and 42 accommodates a rod 45 surrounded by an insulation sleeve 46 which prevents the contact of the rod with the several flat grids arranged thereon in spaced rela-tion face to face. The parts 39 of the grids are maintained insulated from one another or in electrical contact with one another as may be desired by the employment of appropriate insulation or metallic washers 47 surrounding the sleeve 4tlg-nd interposed between these parts of the gri s. l

Thus the portions 39 of the grids are effectively prevented from twisting or warping into Contact relation with one another, their proper separation being assured at all grilles by the employment of the means speci- The insulation washers or the sleeve 46 of each rod 45 in the aligned holes 32 of the group of grids or resistance units are of sufficient size and are of appropriate shape to overlap the sides of the sections 37 or 38, as the case may be, of the grids, thus eliminating the possibility of such parts coming into sidewise contact with one another.

At those points where it is necessary or desirable to effect the electrical connection between the grids, such insulation washers or spacers 48 are recessed to receive slightly spacers 48 on thicker metallic washers 49 of conductive material which by bearing directly on the side faces ot the grids electrically connect them together at such places.

In Figures 3 to 8 inclusive a somewhat modified construction is depicted which, although ot' the same resistance capacity as the structure already described, is of somewhat less width than the grid of Figures 1 and 2 hence effecting a further or additional metal saving on each element manufactured.

In this case, instead of slotting the metal sheet as heretofore indicated, it is in large measure sheared or cut instead of slot-ted, with the metal on opposite Sides of the cuts deformed or deflected out of the plane of the sheet to supply sufficient gaps or spaces between the adjacent parts or strips of the member. l

To this end, the blank is longitudinally slotted parallelly for a short distance inwardly from one end at 50 and 5l and similarly slotted inwardly at the middle of the other end at 52, across slot- 53 being also provided with which the slot 52 connects at its center point. l

The metal plate is then sheared or cut along the tive parallel lines 54, 55, 56, 57. and 58, the lnetal borderingr both sides of each eut being at the same tune bent or deflected in opposite directions to supply between their edges gaps or spaces equivalent to those of the grid of Figure 2.

The parallel, spaced, shear lines 54, 56 and 58 connect with the transverse slot 53, whereas the intermediate parallel cuts'55 and 57 extend inwardly from the inner ends of the pair of slots 5() and 51.

Stated somewhat differently, and as is clearly illustrated, the cuts 54 and 58 begin at the-ends of the cross slot 53 and extend part 'way of the length of the blank, the cuts 55 and 57 forming prolongations of the two parallel spaced slots 50 and 51 and terminating short of the cross slot 53.

The center cut 56 extends inwardly from the transverse slot 53 in line with the slot 52 and ends somewhat short of the corresponding ends of the parallel cuts 54 and 58.

Thus a grid or electrical resistance unit is provided of the same general form as that of Figure 2 and in similar manner the flat ears 59 and 60 are apertured at 61 and holes 62, 63, and 64 are supplied in positions to correspond to holes 42, 43 and 44 respectively of the other species of grids.

The six parallel sections of the grid have been supplied with the reference characters 65 to 70 inclusive and the parts uniting their ends have been denominated 71 to 75 inelusive. all as is clearly shown.

It will be observed from Figure 6 that the inturned terminal ears 59 and 60 are in the same plane in the finished grid, and it will be seen from Figure 7 that the connecting portions 7l and 72 have each a flat intermediate or middle section 76 1n the original plane of the metal sheet whose edge portions T7 and 76 are bent or deflected 1n opposite directions thus provldlng the proper gaps Vor spaces, whereas the s1x par allel strips 6.3 to inclusive` 1n the mlddle portion ot' the grids, are in parallel oblique arrangement as shown in Figure 8 giving the required spaced relation between their longitudinal edges.

These grids are grouped and fastened together in the usual way or in a manner slmilar to that employed for the grldsnof Figures 1 and 2, the parts 71 and 72 being held against sidewise distortion by spacers or washers 79 on the sleeves 80 of the rods or bolts S1 occupying the holes 61 in the flat terminal 59 and 60, such insulation spacers having conductive Washers Where needed to effect the required electrical connections between the grids. Y

The lower portions of the grids are spaced apart and held in fixed relation by means practically like that for the species presented in Figures 1 and 2.

The third form of structure is shown in Figures 9 to 14 inclusive and this is the same as that of Figures 3 to 8 except that instead of employing the slots 50, 51, 52, and 53, corresponding cuts or slits 90 and 91 are substituted for the slots 52 and 53, and in place of the slots 50 and 51 cuts or slits 92 and 93 corresponding to cuts 55 and 57 are made longer and reach to the end of the metal sheet, all as is clearly illustrated in the drawings.

As in the previous instance. the metal at the opposite sides of the plurality of lengthwise cuts is pressed or bent out of the plane of the sheet in opposite directions, whereby the six strips,94 to 99 inclusive present the arrangement shown in Figure 14 with adequate spaces between their lengthwise edges.

The three connecting sections of the metal sheet 100, 101, and 102, apertured -as and for the purpose already specified, are parallel, spaced from one another, and slightly oblique to the plane of the sheet.

The two perforated terminal ears 103 and 104 and the two adjacent connecting parts 105 and 106 are bent so as to be parallel to one another, oblique to the plane of the metal sheet. and spaced away from one another to provide sutiicicnt air gaps between them.

As in the other cases, suitably shaped washers or spacers 107 are employed to separate the parts 105 and 106 of the several associated grids to preclude their coming into contact with one another.

The invention is not limited and restricted to the precise and exact embodiments herein presented and many minor mechanical lchanges may be made in the grids and in their method of production Without departure from the heart and essence of the invention and without the sacrifice of any of its substantial benefits and advantages.

I claim:

1. An electrical resistance grid having a, reflexed strip, the adjacent edge rtions of which are in different planes obl1que to the general plane of the grid.

2. An electrical resistance grid having at one end opposed inwardly-facing termmal ears connected together by a reflexed strip the adjacent edges of which are in different planes.

3. A substantially-rectangular electrical resistance grid having at one end opposed inwardly-facing terminal ears connected together by a reflexed strip the adjacent edges of which are in different planes.

4. ,An electrical resistance grid having a pair of opposite marginal strips equipped at their corresponding ends With inwardlydisposed oppositely-facing terminal ears the other ends of said marginal strips being connected together by a reflexed portion of the grid body, the adjacent edges of which are in different planes.

5. An electrical resistance grid of substantially rectangular shape, having a pair of parallel opposite marginal strips equipped at their corresponding ends With inwardlydisposed terminal ears facing one another, the other ends of said marginal strips being connected together by a refiexed portion of the grid body, the adjacent edges of which are in different planes.

6. A substantially-rectangular electrical resistance grid having a pair of parallel marginal strips equipped at their corresponding ends with inwardly-disposed terminal ears facing one another, the other ends of said marginal strips being connected together by a reflexed portion of the grid body, the adjacent edges of said marginal and relexed strips being in different planes.

7. An electrical resistance grid having a. pair of marginal strips equipped at their corresponding ends wit-h inwardly-disposed terminal ears facing one another and in different planes. the other ends of said marginal strips being connected together by a reflexed port-ion of the grid body` the adjacent edges of said strips and said relexed portion being in different planes.

8. A rheostat comprising a plurality of grids disposed side by side, each of said grids having a pair of marginal strips equipped at their corresponding ends with inwardly-disposed terminal apertured ears facing one another. the other ends of said marginal strips being connected together by a reflexed portion of the grid body positioned Wholly to one side of said pair of ears, rods extended through the apertures in said ears, and means on said rods projecting between and preventin contact of the reflexed portions of the grlds with one another.

9. The method of making an electrical resistance grid comprising shearing a sheetmetal plate to provide terminal ears and a refiexed stri connecting said ears, and bending saidp grid to provide gaps along said shear lines.

10. The method of makin an electrical resistance 'grid comprising s earing a substantially rectangular sheetmetal late to provide a pair of inwardly-dispose oppositely-facing terminal ears at one end anda. refiexed strip con'nectn said ears, the metal on opposite sides o -the cuts forming said reexed strip being bent in opposite directions to provide ga portions of said reflex member.

WM. GUY CLARK.

between the edge 

